RIYADH, 12 August — Health authorities have warned pharmacies against circulating medicines that have a composition other than approved by the quality control centers, saying that these medicines could be harmful to human health.

The sources said the composition of these medicines is changed by adding substances to enhance their effectiveness after the authorities approved their samples. “These changes might have negative effects on users, especially when doctors do not know the changes in their composition,” informed sources said.

The warning was issued after the finding of a false medical preparation, which would have had gross negative effects on health of its users. They said the composition was changed by some companies.

The BBC recently warned against using fake medicines, saying that medical experts at the US and British hospitals had reported deaths caused by such medicines.

Sources at the Health Ministry have expressed fears that such medicines might have found their way into the Kingdom.

Dr. Hamad Al-Aufy, director of the quality control department at the Commerce Ministry, said there are nine main laboratories in addition to their branches under the department.

 to check various products including medicines imported into the country.